Rangers will seek a formal explanation from the Scottish FA following the decision not to send off Auston Trusty for his foul on Jack Butland at Hampden.
The defender kicked Butland in the face late in the first half of the Premier Sports Cup semi-final on Sunday. Referee Nick Walsh awarded a yellow card for the incident, with that call subsequently ratified by the VAR team.
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Rangers were down to ten men at that stage following Thelo Aasgaard's dismissal for a foul on Anthony Ralston. And the decision to only book Trusty became a focal point post-match as Danny Rohl's side slipped to a 3-1 defeat on derby day.
Butland was caught in the head by Trusty after gathering the ball inside the penalty area. And the Rangers Review understands the club will now take the matter to the door of referees chief Willie Collum and the Association to demand answers over the flashpoint.
It is understood that Ibrox chiefs believe that no attempt was made to play the ball and that Trusty endangered the safety of his opponent. As a result, Rangers believe the American should have been dismissed for serious foul play, or potentially violent conduct. Captain James Tavernier revealed that Walsh insisted there was no excessive force in the challenge.
The incident with Trusty came after Aasgaard's dismissal. Rohl did not use that decision from Walsh as an excusive as a Tavernier penalty - which could have seen Ralston pick up a second yellow - took the game to extra time before Celtic emerged as narrow winners at Hampden.
"I didn't watch the red card now back," Rohl said when asked about Aasgaard's red card. "But I think it's the refs, it's not my part to speak about this. I said this before the game that my focus is always on myself, I speak not about the manager or the other team or the refs.
"My focus is really on ourselves, and from this part I saw a team who made huge steps forward in the last seven or eight days, what we put into it, but of course we have other parts we have to improve and this is my job during the week."
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